Abstract
Hybridization of iodinated mouse 5S RNA with Chinese hamster DNA fractionated on a CsCl gradient identified 2 separate DNA components that hybridize with the labeled probe. One component is slightly, and one considerably heavier than the main band DNA. This suggests that the gene coding for 5S RNA in the Chinese hamster may constitute 2 distinct populations differing in guanine + cytosine content of their adjacent spacer regions.